Automated data conversion and route tracking in distributed databases

ABSTRACT

A determination is made as to whether a data type associated with a received logical table definition associated with a database query within a distributed database system differs from a data type associated with a local logical table definition. A data conversion is performed on data retrieved from a locally-stored physical table referenced by the local logical table definition in response to determining that the data types differ. Local data conversion information is created identifying the data conversion performed on the retrieved data in response to performing the data conversion. At least one of the retrieved data and the converted data with the created local data conversion information is forwarded to at least one of a distributed database node and an application-level module.

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under W911NF-06-3-0001awarded by United States Army. The Government has certain rights to thisinvention.

BACKGROUND

The present invention relates to systems and methods for identifyingdata conversion events in distributed databases. More particularly, thepresent invention relates to automated data conversion and routetracking in distributed databases.

Distributed databases include multiple databases accessible via anetwork or other interconnection by a querying computing node. Thedistributed databases may be logically distributed across multipleaccess or network domains and may be geographically distributed acrossphysical locations. The querying computing node often uses a centralizedregistry to identify databases and physical data structures within theidentified databases. The physical data structures are identified andaccessible globally by name. Queries are issued to an identifieddatabase using an identified global name of a physical data structure.Query results are returned from the identified database in response tothe issued query.

SUMMARY

The subject matter described herein provides capabilities for automateddata conversion and route tracking in distributed databases. Logicaldata structures (e.g., table definitions) are transmitted in associationwith a database query within a distributed database system. Upon receiptof the query, a database node determines whether to perform a dataconversion on retrieved local physical data based upon a differencebetween a data type associated with the received logical tabledefinition and a data type associated with a local logical tabledefinition. Data conversion information identifying any data conversionperformed or that no conversion was performed is created to allowtracking of data conversion operations within the distributed databasesystem. The data conversion information is passed on to the originatingnode along with data conversion information received from otherdistributed database nodes. The retrieved local physical data isreturned to the originating node for processing or to anapplication-level module when no conversion is performed. The converteddata and the created data conversion information are forwarded to othernodes for processing or to an application-level module when a dataconversion is performed. The data conversion information may be used byany node to identify where data conversion or casting precision loss orprecision problems occur within the distributed database system. A cacheof queries transmitted and resulting data conversion informationreturned may be maintained and used to identify optimal routes forfuture query transmissions to remove or minimize casting operations.

A method includes determining whether a data type associated with areceived logical table definition associated with a database querywithin a distributed database system differs from a data type associatedwith a local logical table definition; performing a data conversion ondata retrieved from a locally-stored physical table referenced by thelocal logical table definition in response to determining that the datatype associated with the received logical table definition differs fromthe data type associated with a local logical table definition; creatinglocal data conversion information identifying the data conversionperformed on the retrieved data in response to performing the dataconversion; and forwarding at least one of the retrieved data and theconverted data with the created local data conversion information to atleast one of a distributed database node and an application-levelmodule.

A system includes a memory adapted to store data conversion and routetracking information; and a processor programmed to: determine whether adata type associated with a received logical table definition associatedwith a database query within a distributed database system differs froma data type associated with a local logical table definition, perform adata conversion on data retrieved from a locally-stored physical tablereferenced by the local logical table definition in response todetermining that the data type associated with the received logicaltable definition differs from the data type associated with a locallogical table definition, create local data conversion informationidentifying the data conversion performed on the retrieved data inresponse to performing the data conversion, and forward at least one ofthe retrieved data and the converted data with the created local dataconversion information to at least one of a distributed database nodeand an application-level module.

An alternative system includes a memory adapted to store data conversionand route tracking information; and a processor programmed to: determinewhether a data type associated with a received logical table definitionassociated with a database query within a distributed database systemdiffers from a data type associated with a local logical tabledefinition, perform a data conversion on data retrieved from alocally-stored physical table referenced by the local logical tabledefinition in response to determining that the data type associated withthe received logical table definition differs from the data typeassociated with a local logical table definition, create local dataconversion information identifying the data conversion performed on theretrieved data in response to performing the data conversion, add a nodeidentifier to the local data conversion information, determine whetherthe data conversion performed on the retrieved data results in a loss ofprecision associated with the converted data, add local conversionprecision loss tracking information to the local data conversioninformation in response to determining that the data conversionperformed on the retrieved data results in a loss of precisionassociated with the converted data, and forward at least one of theretrieved data and the converted data with the created local dataconversion information to at least one of a distributed database nodeand an application-level module.

Those skilled in the art will appreciate the scope of the presentinvention and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a block diagram of an example of an implementation of a systemfor automated data conversion and route tracking in distributeddatabases according to an embodiment of the present subject matter;

FIG. 2 is a block diagram of an example of an implementation of adatabase management system that is capable of performing automated dataconversion and route tracking based upon propagation of data conversioninformation in association with a database query within a distributeddatabase system according to an embodiment of the present subjectmatter;

FIG. 3 is a block diagram of an example interconnection of componentswithin the system 100 of FIG. 1 to further illustrate an example ofquery processing with data conversion and route tracking according to anembodiment of the present subject matter;

FIG. 4 is a flow chart of an example of an implementation of a processfor automated data conversion and route tracking in distributeddatabases according to an embodiment of the present subject matter;

FIG. 5 is a flow chart of an example of an implementation of a processfor automated data conversion and route tracking in distributed databasesystems by generation of data conversion information in response to dataconversions and data conversion precision loss according to anembodiment of the present subject matter; and

FIG. 6 is a flow chart of an example of an implementation of a processfor automated data conversion and route tracking in distributeddatabases by processing of data conversion information received inresponse to queries issued within a distributed database systemaccording to an embodiment of the present subject matter.

DETAILED DESCRIPTION

The examples set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the invention and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

The subject matter described herein provides capabilities for automateddata conversion and route tracking in distributed databases. Logicaldata structures (e.g., table definitions) are transmitted in associationwith a database query within a distributed database system. Upon receiptof the query, a database node determines whether to perform a dataconversion on retrieved local physical data based upon a differencebetween a data type associated with the received logical tabledefinition and a data type associated with a local logical tabledefinition. Data conversion information identifying any data conversionperformed or that no conversion was performed is created to allowtracking of data conversion operations within the distributed databasesystem. The data conversion information is passed on to the originatingnode along with data conversion information received from otherdistributed database nodes. The retrieved local physical data isreturned to the originating node for processing or to anapplication-level module when no conversion is performed. The converteddata and the created data conversion information are forwarded to othernodes for processing or to an application-level module when a dataconversion is performed. The data conversion information may be used byany node to identify where data conversion or casting precision loss orprecision problems occur within the distributed database system. A cacheof queries transmitted and resulting data conversion informationreturned may be maintained and used to identify optimal routes forfuture query transmissions to remove or minimize casting operations.

The automated data conversion and route tracking in distributeddatabases described herein may be performed in real time to allow prompttracking of data conversions and query route optimization. For purposesof the present description, real time shall include any time frame ofsufficiently short duration as to provide reasonable response time forinformation processing acceptable to a user of the subject matterdescribed. Additionally, the term “real time” shall include what iscommonly termed “near real time”—generally meaning any time frame ofsufficiently short duration as to provide reasonable response time foron demand information processing acceptable to a user of the subjectmatter described (e.g., within a few seconds or less than ten seconds orso in certain systems). These terms, while difficult to precisely defineare well understood by those skilled in the art.

FIG. 1 is a block diagram of an example of an implementation of a system100 for automated data conversion and route tracking in distributeddatabases. Within the system 100, a database management system_1(DBMS_1) 102, a DBMS_2 104, a DBMS_3 106, a DBMS_4 108, a DBMS_5 110, upto a DBMS_N 112 are illustrated. The DBMS_1 102 through the DBMS_N 112are each associated with a database 114, a database 116, a database 118,a database 120, a database 122, up to a database 124, respectively. TheDBMS_1 102 through the DBMS_N 112 are interconnected via a network 126.

For purposes of the present description, it should be noted that whilethe network 126 is illustrated as interconnecting the DBMS_1 102 throughthe DBMS_N 112 with each other, this should not be considered limiting.The network 126 may be formed by any interconnection appropriate for usein a distributed database environment. For example, the network 126 mayinclude any form of interconnection suitable for the intended purpose,including a private or public network such as an intranet or theInternet, respectively, direct inter-module interconnection, dial-up, orany other interconnection mechanism capable of interconnecting thedevices with the system 100.

As such, any two or more of the DBMS_1 102 through the DBMS_N 112 may beinterconnected by proximity, interconnection, or routing capabilitieswithin the system 100, while certain other of the devices may not haveinterconnectivity other than via other distributed database devices.Accordingly, certain of the DBMS_1 102 through the DBMS_N 112 may not becapable of communication with one another other than via the otherdistributed database devices.

As will be described in more detail below in association with FIGS. 2through 6 below, the DBMS_1 102 through the DBMS_N 112 provide automateddata conversion and route tracking within the system 100. The automateddata conversion and route tracking in distributed databases is basedupon propagation of data conversion information identifying dataconversions performed in association with database queries.

It should be noted that the DBMS_1 102 through the DBMS_N 112 may be anytype of device configurable for storage of information and distributedinterconnectivity for database-style queries. For example, the DBMS_1102 through the DBMS_N 112 may include devices such as a personalcomputer (e.g., desktop, laptop, palm, etc.) or a handheld device (e.g.,cellular telephone, personal digital assistant (PDA), email device,music recording or playback device, etc.), or any other device capableof processing information as described above and in more detail below.

FIG. 2 is a block diagram of an example of an implementation of theDBMS_1 102 that is capable of performing automated data conversion androute tracking based upon propagation of data conversion information inassociation with a database query within a distributed database system,such as the system 100. A central processing unit (CPU) 200 providescomputer instruction execution, computation, and other capabilitieswithin the DBMS_1 102. A display 202 provides visual information to auser of the DBMS_1 102 and an input device 204 provides inputcapabilities for the user.

The display 202 may include any display device, such as a cathode raytube (CRT), liquid crystal display (LCD), light emitting diode (LED),projection, touchscreen, or other display element or panel. The inputdevice 204 may include a computer keyboard, a keypad, a mouse, a pen, ajoystick, or any other type of input device by which the user mayinteract with and respond to information on the display 202.

It should be noted that the display 202 and the input device 204 areillustrated with a dashed-line representation within FIG. 2 to indicatethat they are not required components for the DBMS_1 102. Accordingly,the DBMS_1 102 may operate as a completely automated embedded devicewithout user configurability or feedback. However, the DBMS_1 102 mayalso provide user feedback and configurability via the display 202 andthe input device 204, respectively.

A communication module 206 provides interconnection capabilities thatallow the DBMS_1 102 to communicate with other modules within the system100, such as the DBMS_2 104 through the DBMS_N 112, to perform dataconversion and route tracking within the system 100. The communicationmodule 206 may include any electrical, protocol, and protocol conversioncapabilities useable to provide the interconnection capabilities.

A memory 208 includes a matching criteria storage area 210 that storesinformation usable to identify processing preferences or priorities fornon-conflicting queries within the system 100. The matching criteriastored within the matching criteria storage area 210 are used toconfigure and control query data selection and processing, queryforwarding, and query responses. The memory 208 also includes a dataconversion and route tracking storage area 212 that stores dataconversion and route tracking information usable to track dataconversions and to optimize query routing within the system 100. As willbe described in more detail below, the data conversion and routetracking information stored within the data conversion and routetracking storage area 212 is used to track data conversion precisionchanges and data conversion precision loss. The tracked data conversionprecision changes and data conversion precision loss information may beused to optimize routing within a distributed database system, such asthe system 100.

A non-conflicting query propagation module 214 is illustrated. Thenon-conflicting query propagation module 214 provides query processing,query forwarding, and query response capabilities for the DBMS_1 102. Adata conversion and route tracking module 216 is also illustrated. Thedata conversion and route tracking module 216 provides the dataconversion and route tracking capabilities for distributed databasedevices, such as the DBMS_1 102, as described above and in more detailbelow.

Though the communication module 206, the non-conflicting querypropagation module 214, and the data conversion and route trackingmodule 216 are illustrated as component-level modules for ease ofillustration and description purposes, it should be noted that thesemodules include any hardware, programmed processor(s), and memory usedto carry out the respective functions of the modules as described aboveand in more detail below. For example, the communication module 206, thenon-conflicting query propagation module 214, and the data conversionand route tracking module 216 may include additional controllercircuitry in the form of application specific integrated circuits(ASICs), processors, antennas, and/or discrete integrated circuits andcomponents for performing communication and electrical controlactivities associated with the respective modules. Additionally, thecommunication module 206, the non-conflicting query propagation module214, and the data conversion and route tracking module 216 also includeinterrupt-level, stack-level, and application-level modules asappropriate. Furthermore, the modules include any memory components usedfor storage, execution, and data processing for performing processingactivities associated with the respective modules. The communicationmodule 206, the non-conflicting query propagation module 214, and thedata conversion and route tracking module 216 may also form a portion ofother circuitry described without departure from the scope of thepresent subject matter.

The database 114 provides storage capabilities for informationassociated with the automated propagation of non-conflicting queries anddata conversion and route tracking capabilities of the DBMS_1 102. Thedatabase 114 includes a database catalog storage area 218, a logicaltable definition storage area 220, a physical table storage area 222,and an optimized routing storage area 224 that may be stored in the formof tables or other arrangements accessible by the DBMS_1 102.

The database catalog storage area 218 stores information associated withlogical tables stored at other database management systems, such as theDBMS_2 104 through the DBMS_N 112, within the system 100. Theinformation stored within the database catalog storage area 218 may becompiled in response to queries of other database nodes within thesystem 100 for logical table definitions stored at those other nodes. Assuch, the DMBS_1 102 may determine and store logical table definitionsfor other nodes within the system 100 for use during query processing.

The logical table definition storage area 220 stores information aboutlogical tables stored locally to the DBMS_1 102. The logical tables mapto physical data and physical tables stored within the physical tablestorage area 222. The physical table storage area 222 stores physicaltables that may or may not be federated within a distributed databasesystem, such as the system 100, based upon mappings defined within therespective logical table definition storage area 220.

The optimized routing storage area 224 stores information associatedwith preferred and/or optimal routes for distributed database queries asidentified by the data conversion and route tracking module 216. As willbe described in more detail below, logical table definitions areassociated with database queries. Upon receipt of a database query, thereceiving distributed database node, such as the DBMS_1 102, determineswhether a data type associated with the received logical tabledefinition differs from a data type associated with the local logicaltable definition. In response to determining that the data types differ,a data conversion is performed on data retrieved from a stored physicaltable, such as a physical table stored within the physical table storagearea 222. Data conversion information is created to identify the dataconversion performed. If a data conversion has been performed, theconverted data and the created data conversion information are forwardedto at least one of a distributed database node and an application-levelmodule for further processing. If no data conversion has been performed,the retrieved data is forwarded to at least one of a distributeddatabase node and an application-level module for further processing. Anindication that no data conversion was performed may also be propagatedthrough the network.

Additional processing is performed by a receiving node based uponwhether any data conversion information is received in association witha query or a data result set identifying any data conversions performedat any node that processed the query prior to the receiving node, aswill be described in more detail below beginning with FIG. 3. Theoriginating node or any intermediate node may process received andlocally-created data conversion information to track routing andprocessing of queries and to determine whether to reject data from aprevious node or to identify preferred routing for future queries. Thepreferred routing may be stored to the optimized routing storage area224 and may be forwarded to other distributed database nodes todistribute determined route preferences.

It is understood that the memory 208 may include any combination ofvolatile and non-volatile memory suitable for the intended purpose,distributed or localized as appropriate, and may include other memorysegments not illustrated within the present example for ease ofillustration purposes. For example, the memory 208 may include a codestorage area, a code execution area, and a data area without departurefrom the scope of the present subject matter.

The CPU 200, the display 202, the input device 204, the communicationmodule 206, the memory 208, the non-conflicting query propagation module214, the data conversion and route tracking module 216, and the database114 are interconnected via an interconnection 226. The interconnection226 may include a system bus, a network, or any other interconnectioncapable of providing the respective components with suitableinterconnection for the respective purpose.

While the DBMS_1 102 is illustrated with and has certain componentsdescribed, other modules and components may be associated with theDBMS_1 102 without departure from the scope of the present subjectmatter. Additionally, it should be noted that, while the DBMS_1 102 isdescribed as a single device for ease of illustration purposes, thecomponents within the DBMS_1 102 may be co-located or distributed andinterconnected via a network without departure from the scope of thepresent subject matter. For a distributed arrangement, the display 202and the input device 204 may be located at a point of sale device,kiosk, or other location, while the CPU 200 and memory 208 may belocated at a local or remote server. Many other possible arrangementsfor components of the DBMS_1 102 are possible and all are consideredwithin the scope of the present subject matter. It should also beunderstood that, though the database catalog storage area 218, thelogical table definition storage area 220, the physical table storagearea 222, and the optimized routing storage area 224 are shown withinthe database 114, they may also be stored within the memory 208 withoutdeparture from the scope of the present subject matter. Accordingly, theDBMS_1 102 may take many forms and may be associated with manyplatforms.

FIG. 3 is a block diagram of an example interconnection of componentswithin the system 100 of FIG. 1 to further illustrate an example ofquery processing with data conversion and route tracking. It isunderstood that many other types of processing are possible, such asperforming logical table matching, and other processing of queries. Thelogical table matching may be based upon matching criteria, such asmatching criteria stored within the matching criteria storage area 210.Accordingly, all such other possible types of processing are consideredwithin the scope of the present subject matter.

As can be seen from FIG. 3, the general representation of the network126 has been replaced with a connection 302 interconnecting the DMBS_2104 and the DBMS_3 106. Additionally, a connection 304 interconnectingthe DMBS_3 106 and the DBMS_4 108 can also be seen in FIG. 3.

Within FIG. 3, the DBMS_2 104 is shown issuing a “Query1.” The Query1will be described in more detail below. As can be seen from FIG. 3, thelogical table definition storage area 220 of each of the DBMS_2 104through the DBMS_4 108 includes an example logical table definition. Thelogical table definition storage area 220 of the DBMS_2 104 includes alogical table definition of “LT1: a bigint, b varchar.” The logicaltable definition storage area 220 of the DBMS_3 106 includes a logicaltable definition of “LT1: a double, b char.” The logical tabledefinition storage area 220 of the DBMS_4 108 includes a logical tabledefinition of “LT1: a bigint, b char.” Accordingly, the logical tabledefinitions for the respective tables are different at each node thatdefines a given table.

With these example logical table definitions at each node identified,the following detailed query example of data conversion and routetracking elaborates upon the present subject matter. For purposes of thepresent example, the Query1 issued by DBMS_2 104 is assumed to be formedas shown in the following pseudo query format.

-   -   select a,b from logical table ‘LT1’ as LT1 (Query1)

As can be seen from the pseudo query format for Query1, a query isformed using a “select” query identifier. The character or characters(e.g., “a” and “b” within the present example) following the selectquery identifier represents a column name for the associated logicaltable. As such, the Query1 is a column name-based query. Within thepresent example, the Query1 requests data associated with a column named“a” and a column named “b.” The Query1 instructs receiving distributeddatabase nodes to use logical table definitions for fulfillment of therespective queries with the phrase “from logical table” within theQuery 1. The requested logical table is shown within single quotationmarks. As such, each the Query1 requests data associated with logicaltables named “LT1.” The second reference to “LT1” within the Query1 isan alias to a composite name for the logical table, again listed as“LT1” within the present example.

It should be noted that for purposes of the present description, avirtual table interface may be formed based upon the logical tabledefinitions. The virtual table interface may be defined as a set ofinterfaces for representation of physical data for encapsulation andabstraction of the physical data within a distributed network ofdatabases, such as the system 100. Class definitions may be constructedfor creation and representation of the logical table definitions. Forexample, a class for a query may be defined in a syntacticrepresentation, such as in Java™ programming language syntax, to accepta logical table name as an argument of a class constructor. A logicaltable definition may also be passed as a second argument to the classconstructor. Upon instantiation, a query object may be created with thelogical table name and a definition associated with the query object.Distributed database nodes may make calls into the query object forlogical table information and processing.

It should be noted that though the example Query1 associated with FIG. 3does not include communicated matching criteria, it is understood thatthe queries may be modified to include matching criteria withoutdeparture from the scope of the present subject matter. Further,matching criteria may be either communicated with the queries or may bestored locally in advance of issuance of a query. As such, defaultmatching criteria may be established and stored within the matchingcriteria storage area 210 of the memory 208 at each distributed databasenode. For example, default matching may be strict matching for columnname, column position within a logical table, column name data type,column name data precision, and other factors. Issued queries may modifydefault matching criteria to pass additional or alternative matchingcriteria instructing the receiving distributed database nodes to matchbased upon the additional matching criteria or to change defaultmatching criteria. Example additional or alternative matching criteriainclude matching a column name in any position of a logical table,matching data precision based upon equal or greater precision within therespective logical table definitions, and other matching criteria. Thereare many other possible matching criteria that may be used and all areconsidered within the scope of the present subject matter.

Returning to the description of the present example, automated dataconversion and route tracking associated with the Query1 will now bedescribed. As described above, the Query1 is originated by the DBMS_2104. The Query1 is processed internally by the DMBS_2 104 and isautomatically propagated (e.g., forwarded) to other nodes forprocessing. Regarding the internal processing at the DMBS_2 104, theQuery1 is compared with locally-defined logical tables to identify alocal logical table named “LT1.” As can be seen from FIG. 3, a locallogical table named “LT1” is defined within the logical table definitionstorage area 220 of the DBMS_2 104. Accordingly, the Query1 is processedlocally to identify a physical table mapped by the logical table “LT1”within the physical table storage area 222 (not shown) and will resultin the value of data stored within the mapped physical table associatedwith the column “a” and the column “b” in the logical table “LT1” beingreturned from the local database 116.

The DMBS_2 104 also forwards the Query1 to the DBMS_3 106 for processingwith Query1′ as the query name. As described above and in more detailbelow, the DMBS_2 104 includes its logical table definition with theforwarded query. For purposes of the present example, the forwardedQuery1′ is assumed to be formed as shown in the following pseudo queryformat.

select a,b from new logical table ‘LT1’, ‘a bigint, b varchar’ as LT1(Query1′)

As can be seen from the pseudo query format for the forwarded Query1′,the logical table definition of “LT1” associated with the DBMS_2 104 isforwarded as a portion of the forwarded Query1′ to other nodes withinthe system 100.

Referring to the DBMS_3 106, upon receipt of the forwarded Query1′, theDBMS_3 106 performs a variety of operations to forward and fulfill thedata request associated with the forwarded Query1′. The DBMS_3 106determines whether the received logical table definition matches a locallogical table definition and processes matching logical tabledefinitions. As will be described in more detail below, the DBMS_3 106also forwards the query to at least one other distributed database node.In the present example, the DMBS_3 106 forwards the Query1′ to theDBMS_4 108 with Query1″ as the query name. The DBMS_3 106 may also alterthe forwarded logical table definition based upon its processing of thereceived logical table definition. For purposes of the present example,the forwarded Query1′ is assumed to be formed as shown in the followingpseudo query format.

select a,b from logical table ‘LT1’, ‘a double, b char’ as LT1 (Query1″)

While processing at the respective distributed database nodes may beasynchronous and results may be returned when results have beenprocessed at the respective nodes, the present example describessequential processing for ease of illustration purposes. As such, areceiving node other than a final node associated with the query (e.g.,the DBMS_4 108 in the present example) is described as receiving aresult set from a node that it has forwarded a query to prior toresponding to the query it receives. The DBMS_4 108 processes the queryit receives and returns a result set without forwarding the query to anyother node within the present example. It is understood that thisexample processing is for ease of illustration purposes only and anysequence of processing is considered within the scope of the presentsubject matter.

For example, all distributed database nodes may return results and dataconversion information to the originating node and the originating nodemay determine acceptability of data conversions performed and maydetermine associated query route preferences. Alternatively, as with thepresent example, each distributed node may evaluate processing and dataconversions performed by downstream nodes (e.g., nodes that a query wasforwarded to) based upon results returned by the downstream nodes andmay reject or accept data conversions and associate query routepreferences with results returned to the originating node.

In accordance with the present example, processing at the DBMS_4 108will be described before processing at the DBMS_3 106. Accordingly,regarding processing of the Query1″ at the DBMS_4 108, the logical tabledefined in association with the DBMS_4 108 has a logical table named“LT1,” but the data type associated with the column “a” does not matchthe received logical table definition for the logical table “LT1.” Thereceived logical table definition shows that the data type associatedwith the column “a” has a data type of “double.” However, the logicaltable defined in association with the DBMS_4 108 has a data type of“bigint” for the column “a.” It is again noted that the forwardedQuery1″ does not include any matching criteria, but that matchingcriteria could be forwarded with the Query1″ or stored in associationwith the DBMS_4 108 without departure from the scope of the presentsubject matter.

Continuing with the present example, the DBMS_4 108 retrieves a datavalue referenced by the column “a” in the local logical table for “LT1”from an associated physical table storage area 222 (not shown) forprocessing. Based upon the mismatch of the data types for the column“a,” the DBMS_4 108 casts the retrieved data value referenced by thecolumn “a” in the local logical table for “LT1” from the data type“bigint” to the data type “double.” The DBMS_4 108 also creates dataconversion information identifying the data conversion performed on theretrieved data in response to the data conversion performed. The dataconversion information may be created in any suitable form. For purposesof the present example, the form of an “array of operations” may beused. The array of operations may be a one dimensional or amulti-dimensional array of information based upon the information to bestored within the array of operations. As the last node within thepresent example to process the issued query, the DBMS_4 108 forwards theconverted data with the created local data conversion information to atleast one other distributed database node, such as to the DBMS_3 106within the present example, as a Result_Set1″.

The DBMS_3 106 receives the Result_Set1″ from the DBMS_4 108. Asdescribed above, the DBMS_4 108 may have already processed the queryupon receipt of the Result_Set1″. The DBMS_3 106 may also have forwardedits results or may accumulate results for the originating node. Forpurposes of the present example, the DBMS_3 106 accumulates the queryresults for the originating node, makes determinations regarding anydata casting or conversion operations performed by downstream nodes, andidentifies preferences for query route processing. The query routingpreferences may be stored within the optimized routing storage area 224or otherwise for future query routing and processing. As such, theprocessing of the forwarded Query1′ received from the DBMS_2 104described below may have occurred by the time the Result_Set1″ isreceived by the DBMS_3 106.

Regarding processing of the received Result_Set1″, the DBMS_3 106analyzes the returned data conversion information (e.g., an array ofoperations) and makes a determination as to whether the remote dataconversion information identifying at least one data conversionoperation performed by the downstream node is an acceptable dataconversion. The DBMS_3 106 determines whether the data conversionperformed on the data received from the DBMS_4 108 within theResult_Set1″ results in a loss of precision associated with theconverted data that is larger than a configured precision losstolerance. For example, a precision loss tolerance may be configured andstored within the data conversion and route tracking storage area 212 ofthe memory 208. The precision loss tolerance may be based upon apercentage of loss in precision, specific casting between certain datatypes, or any other data precision related criteria. Accordingly, theDBMS_3 106 determines whether the data conversion performed on the datareceived from the DBMS_4 108 within the Result_Set1″ results in a lossof precision beyond the configured precision loss tolerance. Forpurposes of the present example, it is assumed that a cast from type“bigint” to type “double” is acceptable and the DBMS_3 106 accepts thecasting operation performed by the DBMS_4 108.

For a situation where a casting operation were to be consideredunacceptable from a precision loss perspective or other consideration,the DBMS_3 106 may reject the data returned from the DBMS_4 108 and notethe operation and the processing performed by the DBMS_4 108 as anon-preferred route within route tracking information appended to andreturned in association with the data conversion information to theoriginating node. The non-preferred route information may also be storedwithin the optimized routing storage area 224 or the data conversion androute tracking storage area 212 for future reference and use in queryrouting within a distributed database system, such as the system 100.

Regarding processing of the Query1′ at the DBMS_3 106, the logical tabledefined in association with the DBMS_3 106 has a logical table named“LT1,” but the data type associated with both the column “a” and thecolumn “b” do not match the received logical table definition for thelogical table “LT1.” The received logical table definition shows thatthe data type associated with the column “a” has a data type of“bigint.” However, the logical table defined in association with theDBMS_3 106 has a data type of “double” for the column “a.” Regardingcolumn “b,” the received logical table definition shows that the datatype associated with the column “b” has a data type of “varchar,” butthe logical table defined in association with the DBMS_3 106 has a datatype of “char” for the column “b.” It is again noted that the forwardedQuery1′ does not include any matching criteria, but that matchingcriteria could be forwarded with the Query1′ without departure from thescope of the present subject matter.

Accordingly, when the DBMS_3 106 receives the forwarded Query1′, theDBMS_3 106 utilizes any matching criteria stored within the associatedmatching criteria storage area 210 (not shown) to determine whether thereceived logical table definition matches the local logical tabledefinition for “LT1.” Based upon at least one of the data typemismatches between the local “double” data type and the received“bigint” data type for column “a” and the local “char” data type and thereceived “varchar” data type for column “b,” the DBMS_3 106 determinesthat the local logical table definition does not match the receivedlogical table definition. For purposes of the present example, it isassumed that the DBMS_3 106 casts a data value retrieved from the localphysical table storage area 222 (not shown) for the column “a” to thedata type “bigint” from the data type “double” and for the column “b” tothe data type “varchar” from the data type “char.” The DBMS_3 106 alsoperforms a conversion on the data received from the DBMS_4 108.

It should be noted that, based upon the determined mismatch between thereceived and local logical table definitions for “LT1” at either theDBMS_3 106 and the DBMS_4 108, a warning may be issued to theoriginating node. The warning may be formed as a portion of the returneddata conversion information or sent separately from the data conversioninformation without departure from the scope of the present subjectmatter. However, for purposes of the present example, query processingis detailed without warning processing for ease of illustrationpurposes.

Accordingly, the DBMS_3 106 also creates data conversion informationidentifying the data conversions performed on the retrieved data inresponse to performing the data conversions described above. The dataconversion information may be in the form of an “array of operations,”as described above, or any other convenient format. The DBMS_3 106appends the local data conversion information to the data conversioninformation received in the Result_Set1″ from the DBMS_4 108. The DBMS_3106 forwards the locally-converted data including both thelocally-retrieved data and some or all of any data received from theDBMS_4 108, the created local data conversion information, and theremote conversion information to the DBMS_2 104 within the presentexample as a Result_Set1′. If the DBMS_4 108 returns both the originaldata and converted data, the converted data may be operated upon by theDBMS_3 106, without operation upon the original data.

The DBMS_2 104 receives the Result_Set1′ from the DBMS_3 106. Asdescribed above, the DBMS_2 104 may have already processed the queryupon receipt of the Result_Set1′. The DBMS_2 104 may also have forwardedits results or may accumulate results as the originating node. Forpurposes of the present example, the DBMS_2 104 accumulates the queryresults, makes determinations regarding any data casting or conversionoperations performed by downstream nodes, and identifies preferences forquery route processing. The query routing preferences may be storedwithin the optimized routing storage area 224 or otherwise for futurequery routing and processing. As such, the processing of the Query1described below may have occurred by the time the Result_Set1′ isreceived by the DBMS_2 104.

Regarding processing of the received Result_Set1′, the DBMS_2 104analyzes the returned data conversion information (e.g., an array oroperations) and makes a determination as to whether any of the remotedata conversion information identifying at least one data conversionoperation performed by the downstream node is an acceptable dataconversion. The DBMS_2 104 determines whether the data conversion oraggregate of the data conversions performed on the data received fromeither the DBMS_4 108 or the DBMS_3 106 within the Result_Set1′ resultsin a loss of precision associated with the converted data that is largerthan a configured precision loss tolerance. As described above, aprecision loss tolerance may be configured and stored within the dataconversion and route tracking storage area 212 of the memory 208. Theprecision loss tolerance may be based upon a percentage of loss inprecision, specific casting between certain data types, or any otherdata precision related criteria. Accordingly, the DBMS_2 104 determineswhether the data conversion performed on the data received from theDBMS_4 108 or the DBMS_3 106 within the Result_Set1′ results in a lossof precision beyond the configured precision loss tolerance. Forpurposes of the present example, it is assumed that a casts performed bythe respective nodes are acceptable casting operations.

As described above, for a situation where a casting operation were to beconsidered unacceptable from a precision loss perspective or otherconsideration, the DBMS_2 104 may reject the data returned from theDBMS_4 108 or from the DBMS_3 106 and note the operation and theprocessing performed by the respective distributed database node as anon-preferred route within route tracking information appended to andreturned in association with the data conversion information to theoriginating node. The non-preferred route information may also be storedwithin the optimized routing storage area 224 or the data conversion androute tracking storage area 212 for future reference and use in queryrouting within a distributed database system, such as the system 100.

Regarding processing of the Query1 at the DBMS_2 104, as the originatingnode, the DBMS_2 104 defined the logical table definition for thelogical table named “LT1.” Accordingly, no casting operation isperformed within the present example and the data retrieved from localstorage, such as the physical table storage area 222, is appended to thedata received from the DBMS_4 108 and the DBMS_3 106 and returned to anapplication-level task (not shown), such as the data conversion androute tracking module 216, for data processing as a Result_Set1.

Accordingly, the example of FIG. 3 illustrates that distributed databasenodes within a distributed database system, such as the system 100, maydetermine whether a data type associated with a received logical tabledefinition differs from a data type associated with a local logicaltable definition, perform a data conversion on retrieved local physicaldata and data received from nodes to which this node forwarded the queryin response to determining that the data type associated with thereceived logical table definition differs from the data type associatedwith a local logical table definition, create data conversioninformation identifying the data conversion performed on the retrievedphysical data in response to performing the data conversion, and forwardat least one of the retrieved data and the converted data with thecreated data conversion information to at least one other distributeddatabase node and an application-level module for further processing.The distributed database nodes may also determine whether receivedremote data conversion information indicates that a data conversionperformed at a remote distributed database node results in a loss ofprecision that is larger than a configured precision loss tolerance andmay reject any data determined to be associated with a loss of precisionbeyond an acceptable configured tolerance.

FIGS. 4 through 6 below describe example processes that may be executedby distributed database devices, such as the DBMS_1 102 through theDBMS_N 112, to perform the automated data conversion and route trackingassociated with the present subject matter. The example processes may beperformed by modules, such as the data conversion and route trackingmodule 216 and/or the CPU 200, associated with distributed databasedevices. It should be noted that time out procedures and other errorcontrol procedures are not illustrated within the example processesdescribed below for ease of illustration purposes. However, it isunderstood that all such procedures are considered to be within thescope of the present subject matter.

FIG. 4 is a flow chart of an example of an implementation of a process400 for automated data conversion and route tracking in distributeddatabases. At block 402, the process 400 determines whether a data typeassociated with a received logical table definition associated with adatabase query within a distributed database system differs from a datatype associated with a local logical table definition. At block 404, theprocess 400 performs a data conversion on data retrieved from alocally-stored physical table referenced by the local logical tabledefinition in response to determining that the data type associated withthe received logical table definition differs from the data typeassociated with a local logical table definition. At block 406, theprocess 400 creates local data conversion information identifying thedata conversion performed on the retrieved data in response toperforming the data conversion. At block 408, the process 400 forwardsat least one of the retrieved data and the converted data with thecreated local data conversion information to at least one of adistributed database node and an application-level module. Theactivities described above may also be performed on any data returned tothe present database node by nodes to which it forwarded the query.

FIG. 5 is a flow chart of an example of an implementation of a process500 for automated data conversion and route tracking in distributeddatabase systems, such as the system 100, by generation of dataconversion information in response to data conversions and dataconversion precision loss. At decision point 502, the process 500 waitsfor a query to be received. For purposes of the present example, it isassumed that a received query has a logical table definition associatedwith it and that there is a local logical table definition with the samename associated with the distributed database node that receives thequery and that is executing the example process 500. Additionally, thelogical table definitions define data types, as described above,associated with data represented within physical data storage at thedistributed database nodes.

Furthermore, the decision made at decision point 502 may be adetermination that a result set has been received in response to a queryforwarded to another distributed database node, as described above inassociation with the example of FIG. 3, without departure from the scopeof the present subject matter. As further described above in associationwith FIG. 3, a distributed database node that forwards a query may waitto process its data request until a result set is obtained from anydownstream node(s) or may process the data request concurrently withforwarding a query. As such, the determination at decision point 502includes any such events. For the situation where a query is received,it is assumed that the query may be forwarded and a result set may alsobe received at a later time. This additional processing is notillustrated within FIG. 5 for ease of illustration purposes. However, itis understood that any such additional processing is considered withinthe scope of the present subject matter.

When the process 500 makes a determination at decision point 502 that aquery has been received, the process 500 retrieves physical datarequested by the query from a physical table storage location, such asthe physical table storage area 222, at block 504. At decision point506, the process 500 makes a determination as to whether the data typesreferenced within the received logical table and the local logical tablediffer. Alternatively, the process 500 may make this determination basedupon the retrieved physical data without departure from the scope of thepresent subject matter. The data types may differ due to differences indata field bit count, data type representation (e.g., int, char,varchar, etc.), and other factors associated with the data typerepresentations.

When a determination is made at decision point 506 that the data typesdo not differ, the process 500 forwards the retrieved data in responseto the query at block 508 to at least one of another distributeddatabase node or an application-level module. For example, the process500 may forward the retrieved data to another distributed database nodeor to an application-level module within a result set, such as describedabove in association with FIG. 3. The application-level module may beassociated with the data conversion and route tracking module 216 or maybe another process or associated with another module or device withoutdeparture from the scope of the present subject matter. Anapplication-level module may perform route optimization based upon thedata conversion information forwarded from the process 500. An exampleprocess for route optimization is described in association with FIG. 6below. The retrieved data may also be appended to a result set receivedwith the query or received in response to a query forwarded to anotherdistributed database node without departure from the scope of thepresent subject matter. Upon completion of the processing at block 508,the process 500 returns to decision point 502 to await another query orresult set to be received.

Returning to the description of decision point 506, when the process 500makes a determination that the data types differ, the process 500performs a data conversion at block 510. The data conversion may includea promotion of the data type of the retrieved physical data, a demotionof the data type of the retrieved physical data, a cast of the data typeof the retrieved physical data to another data type, or any other dataconversion operation.

At block 512, the process 500 creates data conversion information, suchas an array of operations or other type of data organizationalstructure, including information about the data conversion operationperformed. At block 514, the process 500 retrieves a node identifierassociated with the distributed database node that is executing theprocess 500. At block 516, the process 500 adds the node identifier tothe data conversion information.

At decision point 518, the process 500 makes a determination as towhether the data conversion that was performed results in a dataprecision loss. When a determination is made that the data conversionperformed results in a data precision loss, the process 500 addsconversion loss tracking information to the data conversion informationat block 520. When the conversion loss tracking information has beenadded to the data conversion information or when a determination is madeat decision point 518 that the data conversion performed does not resultin a data precision loss, the process 500 makes a determination atdecision point 522 as to whether any remote conversion information wasreceived with the query or result set that was received.

When a determination is made at decision point 522 that remoteconversion information was not received, the process 500 forwards theconverted data with the data conversion information to at least one ofanother distributed database node or an application-level module forprocessing at block 524. The process 500 returns to decision point 502to await another query or result set to be received.

Returning to the description of decision point 522, when a determinationis made that remote data conversion information was received, theprocess 500 makes a determination at decision point 526 as to whetherany remote precision loss has occurred. Remote precision loss may beindicated within received remote conversion information by inclusion ofconversion loss tracking information. For example, another distributeddatabase node may execute a process similar to the process 500 and addconversion loss tracking information to forwarded data conversioninformation, such as described above in association with block 520.Presence of conversion loss tracking information within the receivedquery or result set may be used by the process 500 to make thedetermination as to whether any remote precision loss has occurred.

When a determination is made at decision point 526 that no remoteprecision loss has occurred, the process 500 appends the created dataconversion information to the received remote data conversioninformation at block 528 and forwards the received and converted dataand data conversion information to at least one other distributeddatabase node or an application-level module for processing at block530. For example, and application-level module may perform routeoptimization based upon the data conversion information forwarded fromthe process 500. An example process for route optimization is describedin association with FIG. 6 below.

Returning to the description of decision point 526, when a determinationis made that remote precision loss has occurred, the process 500 makes adetermination at decision point 532 as to whether the remote precisionloss has exceeded any defined threshold for precision loss. As describedabove in association with FIG. 3, the defined threshold may be basedupon a precision loss tolerance. A precision loss tolerance may be basedupon a percentage of loss in precision, specific casting between certaindata types, or any other data precision related criteria. Accordingly,any approach to defining a threshold for precision loss is consideredwithin the scope of the present subject matter.

When a determination is made at decision point 532 that the remoteprecision loss has not exceeded any defined threshold for precisionloss, the process 500 continues to block 528 and continues processing asdescribed above. When a determination is made at decision point 532 thatthe remote precision loss has exceeded a defined threshold for precisionloss, the process 500 rejects the remote data at block 534 and appends awarning to the data conversion information at block 536. The process 500continues to block 528 and continues processing as described above.However, within the present branch of processing, the process 500 willnot forward the received and rejected data to another distributeddatabase node or an application-level module at block 530, as otherwisedescribed above within the present example. The process 500 returns todecision point 502 to await receipt of another query or result set.

As such, the process 500 provides automated data conversion and routetracking in distributed databases by generation of data conversioninformation in response to data conversions and data conversionprecision loss. The process 500 also determines whether received dataconversion information indicates a remote precision loss exceeds adefined threshold for precision loss. When the process 500 determinesthat remote precision loss exceeds a defined threshold for precisionloss, the process 500 rejects the received remote data and issues awarning within forwarded data conversion information to document thedata conversion tolerance issue. It should also be noted that either thelocal or a received logical table definition may be forwarded at any ofblocks 508, 524, and 530 without departure from the scope of the presentsubject matter.

FIG. 6 is a flow chart of an example of an implementation of a process600 for automated data conversion and route tracking in distributeddatabases by processing of data conversion information received inresponse to queries issued within a distributed database system, such asthe system 100. At decision point 602, the process 600 waits for queryprocessing results, such as a result set, to be received. When adetermination is made at decision point 602 that a result set has beenreceived, the process 600 parses the received result set for dataconversion information at block 604.

At decision point 606, the process 600 makes a determination as towhether any data conversion errors are identified within the receivedresult set. For purposes of the present example, presence of a warningor conversion loss tracking information within the received dataconversion information may be used to determine whether any dataconversion errors have occurred during processing of a query within adistributed database system. When a determination is made that no dataconversion errors are identified within the received result set, theprocess 600 returns to decision point 602 to await receipt of additionalquery processing results.

When a determination is made at decision point 606 that at least onedata conversion error is identified within the received result set, theprocess 600 extracts a node identifier or node identifiers, asappropriate, from the data conversion information for any problemconversions at block 608. At block 610, the process 600 identifies anypreferred routing based upon the received data conversion information.For example, routing preferences may be established to avoid or mitigatedata conversion precision loss for future queries of the same or similardata associated with a logical table definition.

Any defined routing preferences are stored in association with thelogical table definition for the affected data at block 612. Forexample, the routing preferences may be stored within the optimizedrouting storage area 224 in association with a logical table or logicaltables stored within the logical table definition storage area 220.

At decision point 614, the process 600 makes a determination as towhether to distribute the defined routing preferences to otherdistributed database nodes for storage at those distributed databasenodes. It should be noted that routing preferences may also be passedwith a logical table definition associated with a future query.Accordingly, the process 600 may opt to not distribute the definedrouting preferences and return to decision point 602 to await receipt ofanother result set.

When a determination is made at decision point 614 to distribute thedefined routing preferences, the process 600 forwards the routingpreferences to at least one other distributed database node at block616. The process 600 returns to decision point 616 and continuesprocessing as described above.

As such, the process 600 provides automated data conversion and routetracking in distributed databases by processing data conversioninformation received in response to queries issued within a distributeddatabase system. The process 600 identifies preferred routing for futurequeries based upon data conversion errors identified within receiveddata conversion tracking information received in response to issuedqueries. The process 600 may store the defined preferred routing and maydistribute the preferred routing to other distributed nodes within thedistributed database system.

Accordingly, as described above in association with FIGS. 1 through 6,the example systems and processes provide automated data conversion androute tracking in distributed databases. Many other variations andadditional activities associated with automated data conversion androute tracking in distributed databases are possible and all areconsidered within the scope of the present subject matter.

Those skilled in the art will recognize, upon consideration of the aboveteachings, that certain of the above exemplary embodiments are basedupon use of a programmed processor such as CPU 200. However, theinvention is not limited to such exemplary embodiments, since otherembodiments could be implemented using hardware component equivalentssuch as special purpose hardware and/or dedicated processors. Similarly,general purpose computers, microprocessor based computers,micro-controllers, optical computers, analog computers, dedicatedprocessors, application specific circuits and/or dedicated hard wiredlogic may be used to construct alternative equivalent embodiments.

As will be appreciated by one skilled in the art, the present inventionmay be embodied as a system, method or computer program product.Accordingly, the present invention may take the form of an entirelyhardware embodiment, an entirely software embodiment (includingfirmware, resident software, micro-code, etc.) or an embodimentcombining software and hardware aspects that may all generally bereferred to herein as a “circuit,” “module” or “system.” Furthermore,the present invention may take the form of a computer program productembodied in any tangible medium of expression having computer-usableprogram code embodied in the medium.

Any combination of one or more computer usable or computer readablemedium(s) may be utilized. The computer-usable or computer-readablemedium may be, for example but not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,device, or propagation medium. More specific examples (a non-exhaustivelist) of the computer-readable medium would include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a transmission media such as thosesupporting the Internet or an intranet, or a magnetic storage device.Note that the computer-usable or computer-readable medium could even bepaper or another suitable medium upon which the program is printed, asthe program can be electronically captured, via, for instance, opticalscanning of the paper or other medium, then compiled, interpreted, orotherwise processed in a suitable manner, if necessary, and then storedin a computer memory. In the context of this document, a computer-usableor computer-readable medium may be any medium that can contain, store,communicate, propagate, or transport the program for use by or inconnection with the instruction execution system, apparatus, or device.The computer-usable medium may include a propagated data signal with thecomputer-usable program code embodied therewith, either in baseband oras part of a carrier wave. The computer usable program code may betransmitted using any appropriate medium, including but not limited towireless, wireline, optical fiber cable, RF, etc.

Computer program code for carrying out operations of the presentinvention may be written in any combination of one or more programminglanguages, including an object oriented programming language such asJava™, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

The present invention has been described with reference to flowchartillustrations and/or block diagrams of methods, apparatus (systems) andcomputer program products according to example embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in acomputer-readable medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instruction meanswhich implement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide processes for implementing the functions/actsspecified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible exampleimplementations of systems, methods and computer program productsaccording to various embodiments of the present invention. In thisregard, each block in the flowchart or block diagrams may represent amodule, segment, or portion of code, which comprises one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

A data processing system suitable for storing and/or executing programcode will include at least one processor coupled directly or indirectlyto memory elements through a system bus. The memory elements can includelocal memory employed during actual execution of the program code, bulkstorage, and cache memories which provide temporary storage of at leastsome program code in order to reduce the number of times code must beretrieved from bulk storage during execution.

Input/output or I/O devices (including but not limited to keyboards,displays, pointing devices, etc.) can be coupled to the system eitherdirectly or through intervening I/O controllers.

Network adapters may also be coupled to the system to enable the dataprocessing system to become coupled to other data processing systems orremote printers or storage devices through intervening private or publicnetworks. Modems, cable modems and Ethernet cards are just a few of thecurrently available types of network adapters.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present invention. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A computer program product, comprising: anon-transitory computer readable storage medium having computer readableprogram code embodied therewith, where the computer readable programcode when executed on a computer causes the computer to: receive, by alocal sub-system from a remote sub-system of a distributed databasesystem, over a communication network and from a requestor, a databasequery that comprises as received (i) a query select statement to beperformed locally by the local sub-system, and (ii) a remote logicaltable definition that comprises remote logical table element names andelement data type formatting of a remote logical table defined at theremote sub-system; parse the database query to determine logical tabledefinition data indicative of the remote logical table element names andelement data type formatting of the remote logical table definition;determine, by use of the received remote logical table element names andelement data type formatting, whether a data type associated withelement(s) of the remote logical table definition received within thedatabase query and requested by the received query select statementdiffers from a data type associated with element(s) of a local logicaltable definition that comprises matching logical table element names;perform a data conversion on data retrieved from a locally-storedphysical table referenced by the local logical table definition inresponse to determining that the data type associated with the requestedelement(s) of the remote logical table definition differs from the datatype associated with the element(s) of the local logical tabledefinition that comprises the matching logical table element names;create local data conversion information identifying the data conversionperformed on the retrieved data in response to performing the dataconversion; and forward at least one of the retrieved data and theconverted data with the created local data conversion information to atleast one of a distributed database node and an application-levelmodule.
 2. The computer program product of claim 1, where, in causingthe computer to perform the data conversion on the retrieved data, thecomputer readable program code when executed on the computer causes thecomputer to at least one of promote a data type associated with theretrieved data to the data type associated with the received remotelogical table definition, demote a data type associated with theretrieved data to the data type associated with the received remotelogical table definition, and cast a data type associated with theretrieved data to the data type associated with the received remotelogical table definition.
 3. The computer program product of claim 1,where, in causing the computer to create the local data conversioninformation identifying the data conversion performed on the retrieveddata in response to performing the data conversion, the computerreadable program code when executed on the computer causes the computerto add a node identifier of the local sub-system to the local dataconversion information.
 4. The computer program product of claim 1,where the computer readable program code when executed on the computerfurther causes the computer to one of: match, by comparison of theremote logical table definition with local logical table definitions,element(s) of the remote logical table definition requested by the queryselect statement to element(s) of the local logical table definitionthat references a locally-stored physical table against which to performthe query select statement; or determine whether the data conversionperformed on the retrieved data results in a loss of precisionassociated with the converted data.
 5. The computer program product ofclaim 1, where, in causing the computer to create the local dataconversion information identifying the data conversion performed on theretrieved data in response to performing the data conversion, thecomputer readable program code when executed on the computer causes thecomputer to add local conversion precision loss tracking information tothe local data conversion information in response to determining thatthe data conversion performed on the retrieved data results in a loss ofprecision associated with the converted data.
 6. The computer programproduct of claim 1, where the computer readable program code whenexecuted on the computer further causes the computer to: receive remotedata and remote data conversion information in association with thereceived remote logical table definition, where the remote dataconversion information identifies at least one data conversion operationperformed on the received remote data by at least one other node withinthe distributed database system; and perform a data conversion on thereceived remote data in response to determining that the data typeassociated with the received remote logical table definition differsfrom the data type associated with the respective element(s) of thelocal logical table definition that comprise the matching logical tableelement names.
 7. The computer program product of claim 6, where, incausing the computer to create the local data conversion informationidentifying the data conversion performed on the retrieved data inresponse to performing the data conversion, the computer readableprogram code when executed on the computer causes the computer to appendthe created local data conversion information to the received remotedata conversion information.
 8. The computer program product of claim 7,where the computer readable program code when executed on the computerfurther causes the computer to respond to the database query with atleast one of the retrieved data and the converted data with the createdlocal data conversion information, the received remote data conversioninformation with the appended local data conversion information, and atleast one of the received remote data and the converted remote data tothe at least one of the distributed database node and theapplication-level module.
 9. The computer program product of claim 6,where the computer readable program code when executed on the computerfurther causes the computer to: determine whether the received remotedata conversion information comprises remote conversion precision losstracking information; determine whether the data conversion performed onthe received remote data results in a loss of precision that is largerthan a configured precision loss tolerance based upon the receivedremote conversion precision loss tracking information; and reject thereceived remote data in response to determining that the data conversionperformed on the received remote data is larger than the configuredprecision loss tolerance.
 10. The computer program product of claim 6,where the computer readable program code when executed on the computerfurther causes the computer to identify preferred query routing withinthe distributed database system that minimizes future data castingoperations based upon the received remote data conversion information.11. A computer program product, comprising: a non-transitory computerreadable storage medium having computer readable program code embodiedtherewith, where the computer readable program code when executed on acomputer causes the computer to: receive, by a local sub-system of adistributed database system, a local table definition defining a localtable of data, the local table definition including informationindicative of: (i) a plurality of local table element names, and (ii)for each local table element name of the plurality of local tableelement names, a respectively corresponding data type; receive, by thelocal sub-system, from a remote requestor sub-system of the distributeddatabase system, a database query that includes: (1) a query selectstatement including information indicative of requested data from thelocal table of data, and (2) a remote requestor table definitionincluding information indicative of: (a) a plurality of remote requestortable element names, and (b) for each remote requestor table elementname of the plurality of remote requestor table element names, arespectively corresponding data type; determine that a first remoterequestor table element name, included in the query select statement,corresponds to a first local table element name; retrieve raw queryresponse data from the local table of data, with the raw query responsedata being data that is responsive to the query select statement, andwith the raw query response data including raw first element datacorresponding to the first local table element name; determine that adata type corresponding to the first local table element name does notmatch a data type corresponding to the first remote requestor tableelement name; and responsive to the determination that the data typecorresponding to the first local table element name does not match thedata type corresponding to the first remote requestor table elementname, convert the raw first element data, having the data typecorresponding to first local table element name, to converted firstelement data, having the data type corresponding to the first remoterequestor table element name.
 12. The computer program product of claim11, where the computer readable program code when executed on thecomputer further causes the computer to: responsive to the conversion ofthe raw first element data of the raw query response data, create firstconversion information identifying the conversion of the raw firstelement data of the raw query response data; and send, by the localsub-system, over a communication network and to a destination device,the raw query response data and the first conversion information. 13.The computer program product of claim 11, where the computer readableprogram code when executed on the computer further causes the computerto: replace the raw first element data of the raw query response datawith the converted first element data to obtain converted query responsedata; responsive to the conversion of the raw first element data of theraw query response data, create first conversion information identifyingthe conversion of the raw first element data of the raw query responsedata; and send, by the local sub-system, over a communication networkand to a destination device, the converted query response data and thefirst conversion information.
 14. A system, comprising: a memory; and aprocessor programmed to: receive, by a local sub-system of a distributeddatabase system, a local table definition defining a local table ofdata, the local table definition including information indicative of:(i) a plurality of local table element names, and (ii) for each localtable element name of the plurality of local table element names, arespectively corresponding data type; receive, by the local sub-system,from a remote requestor sub-system of the distributed database system, adatabase query that includes: (1) a query select statement includinginformation indicative of requested data from the local table of data,and (2) a remote requestor table definition including informationindicative of: (a) a plurality of remote requestor table element names,and (b) for each remote requestor table element name of the plurality ofremote requestor table element names, a respectively corresponding datatype; determine that a first remote requestor table element name,included in the query select statement, corresponds to a first localtable element name; retrieve raw query response data from the localtable of data, with the raw query response data being data that isresponsive to the query select statement, and with the raw queryresponse data including raw first element data corresponding to thefirst local table element name; determine that a data type correspondingto the first local table element name does not match a data typecorresponding to the first remote requestor table element name; andresponsive to the determination that the data type corresponding to thefirst local table element name does not match the data typecorresponding to the first remote requestor table element name, convert,within the memory, the raw first element data, having the data typecorresponding to first local table element name, to converted firstelement data, having the data type corresponding to the first remoterequestor table element name.
 15. The system of claim 14, where theprocessor is further programmed to: responsive to the conversion of theraw first element data of the raw query response data, create, withinthe memory, first conversion information identifying the conversion ofthe raw first element data of the raw query response data; and send, bythe local sub-system, over a communication network and to a destinationdevice, the raw query response data and the first conversioninformation.
 16. The system of claim 14, where the processor is furtherprogrammed to: replace the raw first element data of the raw queryresponse data with the converted first element data to obtain convertedquery response data; responsive to the conversion of the raw firstelement data of the raw query response data, create, within the memory,first conversion information identifying the conversion of the raw firstelement data of the raw query response data; and send, by the localsub-system, over a communication network and to a destination device,the converted query response data and the first conversion information.